This invention generally relates to semiconductor structures, and more particularly to semiconductor structures in wireless communication systems that use radio frequency (RF) signals.
Wireless communication systems, such as cellular telephones, that use RF signals, are often made as physically compact as possible. Correspondingly, semiconductor structures in wireless communication systems are often investigated for possible miniaturization.
A possible method for miniaturization is to incorporate as many semiconductor structures as possible into one integrated circuit. In this way, the number of external connections decreases and the area of the semiconductor structures also decreases. In order to incorporate the semiconductor structures onto one die, a composite semiconductor structure may be required.
For RF signals in the microwave spectrum (i.e. 2.1 GHz to 2.7 Ghz) which are widely used in wireless communication systems, compound semiconductor technology, for example, gallium arsenide (GaAs) technology, may be favored. Factors to be considered in selecting compound semiconductor technology may include switching speeds, parasitic capacitances, and ON resistance. For other functions in wireless communication systems, non-compound semiconductor technology such as silicon-based transistors may be favored.
However, manufacturing an integrated circuit from a composite semiconductor structure incorporating both GaAs and silicon technology, has been difficult. For example, it has been difficult to overlay a high quality compound semiconductor (GaAs) layer over a high quality monocrystalline silicon substrate.
What is needed is to reduce the difficulty of providing wireless communications components in a smaller number of integrated circuits by integrating the components into composite semiconductor structures.